Electrophoresis is a method used to separate and analyze biological macromolecules, including proteins, DNA, RNA, and complexes of these molecules. Numerous electrophoretic techniques have been developed including capillary electrophoresis, gel electrophoresis, paper electrophoresis, and immunoelectrophoresis.
A common electrophoretic method is gel electrophoresis. In gel electrophoresis, a gel is formed using compounds such as agarose or polyacrylamide. A mixture containing the desired compound(s) is placed (or loaded) onto one end of the gel, and the gel is then placed contact with a liquid buffer. This liquid buffer contains salts, which, when dissolved, form ions within the buffer.
Biological molecules are typically charged, for example when contacted with electrophoresis buffer. For example, DNA is negatively charged in common electrophoresis buffers due to the phosphate groups in its backbone. Therefore, when electric current is applied to the ends of the gel, the biological molecules move through the gel from one end to the other. Depending on their size, shape, and charge, some molecules move through the gel faster than others. As the mixture moves through the gel, molecules of one size, shape, or charge are separated from those of a different size, shape, and/or charge. The speed at which the molecules pass through the gel and the separation between the various types of molecules also depends on the concentration and type of the gel. In general, molecules pass through thicker gels slower than they do through thinner gels, though thicker gels typically provide better separation.
The gels can be run horizontally and/or vertically. When run horizontally, the gel is generally submerged in the buffer. The sample mixture is loaded at one end and run to the other end. When the gel is run vertically, the sample mixture is loaded at the top of the gel and run towards the bottom. A vertical gel is generally not submerged in buffer. Rather it is run on an electrophoresis apparatus that contains a buffer chamber at the top and the bottom of the gel.
Conventional electrophoresis apparatus include cassettes that are typically two parallel glass plates held apart by spacers. Separation of biomolecules within an electrophoresis gel is easily achieved; however, subsequent collection of the isolated molecules for further analysis can be inefficient and difficult. This is especially true when the individual biomolecules or complexes containing the biomolecules have different physical characteristics, such as molecular weights and/or charges. For example, in traditional gel electrophoresis, as a mixture of biomolecules moves through the gel, molecules of one size, shape, or charge are separated from those of a different size, shape, and/or charge. Thus, biomolecules of interest can be spread apart within the cross-linked gel, leaving them not easily accessible. There thus remains a need for improved electrophoresis apparatus that addresses these and other issues.